Antenna switching system



April 29, 1952 w MARCHETT] 2,594.328

' ANTENNA SWITCHING SYSTEM Filed June 27, 1945 2 SHEET.$SHEET 1 an IL 17 INVENTOR. JOHN W. MARCHETTI BY WMQ/Au ATTORNEY FIG. 2.

April 29, 1952 Filed June 27, 1945 J. W. MARCHETTI ANTENNA SWITCHING SYSTEM 2 SHEETSSHEET 2 ANTENNA\ SHAFT r |OO'\:

REVERSING SWITCH [o4 FIG. 4.

INVENTOR.

JOHN W. MARCHETTI w e 41., i -a I L ATTORNEY Patented Apr. 29, 1952 ANTENNA SWITCHING SYSTEM John W. Marchetti, Oceanport, N. J., assignor to the United States of America as represented by the Secretary of War Application June 27, 1945, Serial No. 601,907

6 Claims.

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 O. G. 757) The invention described herein may be manu factured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

My present invention relates to antennas, and more particularly, to an antenna for a pulse echo radio system for object-detection. The present application is a continuation in-part of my application entitled Antenna, Serial No. 545,799 filed July 20, 1944, Patent No. 2,474,854, issued on July 5, 1949.

In systems of the general character indicated, especially those designed for early warning, it is necessary that the angle of radiation of the transmitted energy be kept low. Existing antennas capable of satisfying this requirement have done so only at the sacrifice of higher angle coverage, and the undesirable creation of gaps or null zones due to ground reflection.

It is therefore the main object of my present invention to provide an antenna, particularly, but not exclusively, for an early-warning, objectdetecting radio system, which overcomes the above-described disadvantages, enables adequate coverage throughout a relatively large elevational angle commencing substantially at the horizontal.

It is a further object of my present invention to provide an antenna, having the foregoing highly desirable characteristics, which is simple in construction, easy and economical to fabricate and assemble, and adapted to perform its intended functions in an eflicient manner.

These, and other objects and advantages of my present invention, which will be better understood as the detailed description thereof progresses, are attained, broadly, in the following manner:

I provide an antenna consisting of a radiating head, and a parabolic reflector. The head preferably includes a plurality of horizontallypolarized, half-wave dipole elements vertically stacked in the focal plane of the parabola.

The radiating elements are so fed that, at the will of the operator, the parabola can be subjected to phase or anti-phase illumination. If the former, maximum energy is concentrated at and reflected from the center of the parabola,

with a tapering off toward the outer periphery,

and minor concentrations intermediate the center and the upper and lower regions of the refleeting surface. If the latter, there are two maxima of energy out of phase with each other, one occuring near each of the upper and lower regions of the dish, with minor concentrations on each side of said maxima, and a minimum at the center.

With phase illumination, most of the energy is at a low angle and broken up into approximately equal maximum and minimum zones. With anti-phase illumination, most of the energy zones are at higher angles with maximum and minimum zones which dovetail with the maxima and minima of phase illumination.

In the accompanying specification there is described, and in the annexed drawings shown, what is at present considered a preferred embodiment of the antennas of my present invention. It is, however, to be clearly understood that my present invention is not limited to said embodiment, inasmuch as changes therein may be made without the exercise of invention and within the true spirit and scope of the claims hereto appended.

In said drawings, Figure 1 is a fragmentary, partial front elevation, partial transverse section of an antenna made in accordance with the principles of my present invention;

Figure 2 is a perspective view of the radiating head thereof;

Figure 3 is an example of the vertical coverage patterns obtained with my present invention, utilizing the aforementioned phase and antiphase illumination; and

Figure 4 is a diagrammatic showing of a modification of my invention.

Referring now more in detail to the aforesaid preferred embodiment of my present invention, with particular reference to Figures 1 and 2 of the drawings, the numeral 5 generally designates an antenna, comprising a radiating head 1 centrally disposed in the focal plane of a parabolic reflector 6.

The head 1' preferably includes three vertically stacked, horizontally-polarized, half-wave radiating dipoles 8, 9, and I0, and three similarly disposed and polarized parasitic reflecting elements ll, [2, and I3, located at an appropriate distance in advance of said radiating dipoles to prevent direct radiation from said dipoles in the forward direction.

Each of said radiating dipoles and each of said reflecting elements includes a pair of oppositely directed quarter-wave members [4, the members of each of said pairs extending outwardly from coaxial transmission lines l8, l9, and 20.

The outer conductors of said transmission lines are each provided with slots 2|, whereby the points, at which the oppositely extending quarter- 3, Wave members of each radiating dipole are connected, present a matched impedance.

The transmission lines l8, l9, and 20 also include inner conductors 22, 23, and 24, the outer ends of said conductors being electrically connected, by elements 25, to one of the quarterwave members Id of the appropriate radiating dipole, with the dipole 8 fed 180 out-of-phase with the dipole Ill, as shown.

The inner ends of said inner conductors 22, 23, and 24 terminate equi-distantly from a pivot 26 on which is mounted a switching blade 21. The pivot is rotatably carried in the split end of an inner conductor 28 of a main coaxial transmission line 29 adapted to convey radio-frequency energy from a transmitter (not shown) to the radiating head 7, the outer conductor 36 of said transmission line being connected, directly, to the outer conductor [6, and being connected to the outer conductors l and IT,

respectively, through sections 3! and 32.

The pivot 26 and the blade 2? carried thereby are adapted to be rotated through 90 by a small reversible electric motor 33 fed through a cable 35, the arrangement being such that, in one position of the blade 27, energy is simultaneously conveyed to the dipoles 8 and ill, and in the other position of said blade, energy is conveyed only to the dipole 9. The position of the blade is intended to be under the control of the operator of the aforementioned detecting system.

It will be noted that when the dipole 9 is energized, all of the energy illuminating tr e parabola 6 is in-phasc, but when the dipoles B and ID are energized because of the opposite connections, through the elements 25, of the inner conductors 22 and 25 to the quarter-wave members it of said dipoles 8 and iii, the parabola is subjected to anti-phase illumination.

Now, in Figure 3 of the drawings, I have shown, in full lines, the coverage patterns of the energy lobes (for radiation at 600 megacycles), which exist when the switch blade 2? is in such position that the parabola 6 is subjected to phase illumination, and I have also shown, in broken lines, the coverage patterns of the energy lobes obtained when the switch is in a position to subject the parabola to anti-phase illumination. It will be noted that the main lobe obtained with phase illumination is disposed at a very low angle from the horizontal, in the neighborhood of 2, while the minor lobe is disposed at an angle of about 6. Higher angle coverage is completely lacking, and there is a null zone of considerable extent between the major and minor lobes. However, when anti-phase illumination is resorted to, a greater total number of energy lobes is obtained, covering the region of space intermediate about 4 from the horizontal and about 15 from the horizontal, with said lobes filling the null zones present when phase illumination is used.

Reference is now made to Figure 4 which shows a modification or my invention, in which the switching is done automatically in response to the rotation of the antenna. The antenna shaft loll is continuously rotated by means of a. motor I92. Fixed or otherwise coupled to the antenna shaft for rotation therewith, is a cam I04 which, at every revolution of the antenna, operates the actuating button list of a motor reversing switch Hi8, which is connected to switching motor 33 through cable 3Q. Thus, at every revolution of antenna shaft its, switch I08 will be actuated to reverse motor which will alternately connect the dipoles in phase and anti-phase relation.

4 If desired, the automatic reversing feature can be combined with manual control to render the equipment more flexible.

It Will thus be noted that by means of the present invention, I am able to eliminate the disadvantages associated with antennas heretofore designed for early-warning object-detecting systems, namely, the lack of higher angle coverage, and the existence of extensive null zones within the region of space intended to be covered by the system. It will further be noted that by means of my present invention I am able to obtain adequate coverage throughout an elevational angle of considerable extent, commencing not much above the horizontal; and that the means er-- ployed to attain this highly desirable result are simple in construction, and easy to manufacture and use.

Other objects and advantages of my present invention will readily occur to those skilled in the art to which the same relates.

I claim:

1. In combination, a directional antenna array comprising, a plurality of dipoles, a transmission line, a first connection to connect at least two of said dipoles in opposite phase to said transmission line, a second connection to connect at least one other in the same phase as one of said oppositely phased dipoles, and switching means for alternately selecting said first and second connections, means for rotating said antenna array through a predetermined azimuth angle, and means responsive to the rotation of said antenna array for operating said switching means upon successive rotations of said antenna array through the same azimuth angle.

2. An antenna array as set forth in claim 1, wherein said predetermined azimuth angle is 369.

3. An antenna array comprising; a parabolic reflector, a plurality of dipoles disposed in the focal plane of said reflector, a transmission line having a first branch coupled to at least two of said dipoles in opposite phase and a second branch coupled to at least one other dipole in the same phase as that of one of said oppositely phased dipoles, switching means for alternately selecting said branches, means to continuously rotate said antenna array, and means co-operating with said rotating means to operate said switch means upon successive rotations of said antenna array through a'predetermined azimuth angle.

4. An antenna array as set forth in claim 3 wherein said predetermined azimuth angle 360.

5. In an early warning radar system, an antenna arrangement adapted to provide a wide, continuous vertical angle coverage beginning from a relatively low angle, said antenna arrangement comprising a single parabolic reflector; a first radiating dipole located at the intersection of the axis and the focal plane of said reflector; second and third radiating dipoles located in said focal plane on opposite sides of saidaxis; a branched coaxial transmission line for feeding said second and third dipoles in opposite phase and for feeding said first dipole in the same phase as that of one of said second or third dipoles, the outer conductors of the branches of said transmission line being slotted to determine the impedance presented to the points at which the elements of each of said dipoles are connected; a source of radio energy; switching means for connecting the branches of said transmission line to said source of radio energy so that, alternately, said first radiating dipole is energized and then said second and third radiating dipoles are simultaneously energized; means to continuously rotate said antenna arrangement; and means co-operating with said rotating means to operate said switch means upon successive rotations of said antenna arrangement has been rotated through a predetermined azimuth angle.

6. An antenna arrangement as set forth in claim 5 wherein said predetermined angle is 360.

JOHN W. MARCHETTI.

REFERENCES CITED The following references are of record in the file of this patent:

Number 10 Number UNITED STATES PATENTS Name Date Ilberg May 2, 1939 Gerhard Jan. 16, 1940 Usselman Mar. 11, 1941 Marchetti July 5, 1949 Barrow et al Sept. 6, 1949 FOREIGN PATENTS Country Date Germany Sept. 16, 1935 Germany Apr, 30, 1941 

